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https://issues.apache.org/jira/browse/HADOOP-6350?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14027170#comment-14027170
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Akira AJISAKA commented on HADOOP-6350:
---------------------------------------
Thanks [~arpitagarwal] for the review!
bq. I am not sure what this means - Each metrics record contains tags such as
ProcessName, SessionId, and Hostname as additional information along with
metrics.. How are these tags accessed, I don't see them in jconsole? Perhaps I
am missing some basic knowledge, let me know if so.
I can see them from jmx as follows:
{code}
"name" : "Hadoop:service=NameNode,name=FSNamesystem",
"modelerType" : "FSNamesystem",
"tag.Context" : "dfs",
"tag.HAState" : "active",
"tag.Hostname" : "trunk",
"MissingBlocks" : 0,
"ExpiredHeartbeats" : 0,
...
{code}
Metrics records contain tags for grouping on host/queue/username etc.
{quote}
Namenode - snapshot metrics are missing.
DataNode - DataNodeInfo metrics are missing.
DataNode - FsDatasetState metrics are missing.
{quote}
These are not actually metrics. These are not collected or sinked by
{{MetricsSystem}}, so users cannot get them by file or ganglia. Users can get
these information only by jmx/jconsole.
bq. Nitpick: we should use title case consistently for sub-headings e.g.
rpcdetail --> RpcDetailed
The title shows the name of the Metrics, so it can be case inconsistent if the
name is inconsistent. For example, the name "namenode" is set by the following
code (NameNodeMetrics.java) :
{code}
final MetricsRegistry registry = new MetricsRegistry("namenode");
{code}
> Documenting Hadoop metrics
> --------------------------
>
> Key: HADOOP-6350
> URL: https://issues.apache.org/jira/browse/HADOOP-6350
> Project: Hadoop Common
> Issue Type: Improvement
> Components: documentation, metrics
> Affects Versions: 3.0.0, 2.1.0-beta
> Reporter: Hong Tang
> Assignee: Akira AJISAKA
> Labels: metrics
> Attachments: HADOOP-6350-sample-1.patch, HADOOP-6350-sample-2.patch,
> HADOOP-6350-sample-3.patch, HADOOP-6350.4.patch, HADOOP-6350.5.patch,
> HADOOP-6350.6.patch, HADOOP-6350.7.patch, sample1.png
>
>
> Metrics should be part of public API, and should be clearly documented
> similar to HADOOP-5073, so that we can reliably build tools on top of them.
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